(1) Field of the Invention
The present invention relates to a film or sheet composed of a laminate comprising a layer of a specific resin and a paper layer, and a box-shaped vessel (hereinafter referred to as "carton") prepared from this film or sheet.
More particularly, the present invention relates to a film or sheet having an excellent oil and fat impermeability, which is composed of a laminate comprising a layer of poly-4-methyl-1-pentene having a melting point within a specific range and a paper layer, or a laminate comprising a layer of ordinary poly-4-methyl-1-pentene, an intermediate layer of a specific resin and a paper layer, and also to a carton prepared from this film or sheet.
(2) Description of the Related Art
Recently, the cooking method using an electronic oven has made a rapid progress, and a variety of foods such as dishes and cakes can be easily prepared by using an electronic oven.
When a food is cooked by an electronic oven, the food to be cooked is contained in a tray-shaped vessel formed of a laminate comprising, for example, an inner layer of a 4-methyl-1-pentene polymer and an outer paper layer, and the food is subjected to high-frequency heating.
Foods to be cooked include foods containing oil and fat components such as butter and margarine, for example, pound cakes, and foods on which a sauce containing oil and fat components is poured to complete cooking after heating, and it sometimes happens that after heating in an electronic oven or after pouring of a sauce containing oil and fat components after side heating, foods are preserved in a box-shaped vessel.
Since the heretofore used covering layer of a 4-methyl-1-pentene polymer has a high rigidity, fine cracks are sometimes formed in the covering layer. Moreover, when oil and fat components as described above are present, they permeate into the paper layer constituting the vessel with the lapse of time, the paper layer as a whole becomes oily to degrade the appearance of the vessel, and there is a risk of contamination of the hand or clothing with oil and fat components at the time of handling.